Red blood cells have been labeled with technetium-99m and used in nuclear medicine for red cell volume determinations, placenta localization, cardiac imaging and blood flow studies, and after heat denaturation for spleen imaging.
Both in vitro and in vivo methods have been disclosed for labeling red blood cells with technetium-99m, and both methods employ stannous ion for the reduction of the pertechnetate ion. This reduction appears to be necessary for satisfactory labeling of red blood cells. As reported in the literature, the amount of stannous ion utilized in these procedures is critical; see, for example, U.S. Pat. No. 3,988,429 and J. Nucl. Med., 18: 305-308.
In vivo labeling of red blood cells utilizes intravenous injections of stannous ion followed by technetium-99m as the pertechnetate ion. This methodology has proven to be convenient and results in about 90% labeling efficiency (labeling efficiency refers to the percentage of available technetium-99m associated with red blood cells. The red blood cells labeled in vivo cannot, however, be used for blood volume measurements and spleen imaging.
Various methods for the in vitro labeling of red blood cells with technetium-99m have been disclosed in the literature; see, for example, J. Nucl. Med. Tech., 5: 32-34. The methods disclosed utilize a sterile pyrogen free container such as a plastic bag, partially evacuated collecting tube, or syringe.
U.S. Pat. No. 3,988,429 and J. Nucl. Med., 17: 126-132 disclose a relatively simple kit for the in vitro labeling of red blood cells. The kit disclosed is available commercially from Brookhaven National Laboratories. As disclosed in the patent, the amount of technetium-99m label used is limited.